We propose to conduct a pilot, double-blind, placebo-controlled, randomized clinical trial to treat acute ischemic stroke with a promising new anti-thrombotic agent, the platelet glycoprotein (GP) IIb/IIIa receptor inhibitor abciximab, and to employ a combination of clinical and novel MRI outcome measures, with the ultimate goal of integrating MRI technology into Phase II/III clinical trials of treatment of acute ischemia stroke. We expect that the data derived from this study will help determine whether treatment with abciximab in the acute phase of ischemic stroke results in improved early and chronic neurological outcome. This trial will also seek to define MRI surrogate markers of activity of t his therapeutic agent and to correlate clinical outcome assessment parameters with pre- and post-treatment MRI measures. MRI markers will be sought to discriminate those patients who are likely to respond to therapeutic agent from those who are unlikely to respond to the therapeutic agent because of advanced brain tissue injury. We believe that the results from the present study will lead to substantial improvements in the design and efficient of subsequent Phase II or III therapeutic clinical trials of acute ischemic stroke.